Thanks for all the answers.
At this moment i have a EFS 55-250 IS and the zoom range works fine for aircraft taxing and on take off roll, this is in my nearby airport OPO. The big disadvantage for me of the EF 70-200 f2.8 is the weight, a couple of hours with that on my arms and at the moment i have a 500d so a big lenses with a small body don't know.... The IS in the lenses is useful for me to trie some new shots and because i use my camera 70% for plane-spotting and the other 30% for travel or general photos.
I'm also a big fan of the EF 100-400 L IS but its an old lenses that someday would have a replacement? I also been searching stuff about the EF 70-300 L IS and it seems to be good material, at this moment my budget its around â‚¬1100 so i'm seriously thinking about buying the EF 70-200 F4 L IS and later with more â‚¬ available and a new body i would like to have a lenses like the EF 100-400 L IS and the EF 70-200 f2.8 L IS II
In our single airport in the country, there is a particular spot for plane-spotters, and I do go there sometimes just to watch them, and the planes while eating something. Most of them use any type of lenses, and even smaller cameras. 70-200, 100-400 and 70-300, 55-250 are the most common, and pretty much every lens seems to deliver for them. They told me that usually their objective is to collect the different planes including different serial no's, and that sometimes they only shoot the serial numbers or stickers.
I have seen your photos and it seems that you are doing well with your setup. Do you have a particular shortcoming with the 55-250 for your needs ? I am asking as this can help you further, to decide what's best way forward.